[PATCH 2/2] nbd/proto: add NBD_CMD_WRITE_ZEROES64

[Vladimir Sementsov-Ogievskiy]

Add new structured request type to represent 64bit version of
NBD_CMD_WRITE_ZEROES.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 doc/proto.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/doc/proto.md b/doc/proto.md
index cb0ac56..378a800 100644
--- a/doc/proto.md
+++ b/doc/proto.md
@@ -1096,6 +1096,8 @@ The field has the following format:
   is set.
 - bit 12, `NBD_FLAG_STRUCTURED_REQUEST`; allow clients to use
   structured requests.
+- bit 13, `NBD_FLAG_SEND_WRITE_ZEROES64`: documents that the server
+  understands `NBD_CMD_WRITE_ZEROES64` structured request chunk type.
 
 Clients SHOULD ignore unknown flags.
 
@@ -1866,6 +1868,25 @@ NBD_STRUCTURED_FLAG_DONE (NBD_NONE_CHUNK may be used for 
this).
   represents a no-op command, which SHOULD be replied with no errors and
   may be used like ping, to check server availability.
 
+* `NBD_CMD_WRITE_ZEROES64` (6)
+
+  NBD_CMD_WRITE_ZEROES representation with 64bit length.
+
+  The payload is structured as:
+
+  16 bits: command flags
+  64 bits: offset (unsigned)
+  64 bits: length (unsigned)
+
+  The fields has exactly same meaning as corresponding fields for
+  NBD_CMD_WRITE_ZEROES request.
+
+  This request chunk type MUST be the only one chunk of the structured message
+  and therefore MUST be accompanied by NBD_STRUCTURED_FLAG_DONE.
+
+  This request chunk type is negotiated by server flag
+  NBD_FLAG_SEND_WRITE_ZEROES64, and MUST not be used otherwise.
+
 #### Request types
 
 The following request types exist:
@@ -2138,6 +2159,11 @@ The following request types exist:
     including one or more sectors beyond the size of the device. It SHOULD
     return `NBD_EPERM` if it receives a write zeroes request on a read-only 
export.
 
+    If structured requests are negotieated by server, client MAY use
+    64bit variant of the command, which has exactly same behavior and
+    the only differency is 64bit length field. See NBD_CMD_WRITE_ZEROES64
+    above.
+
 * `NBD_CMD_BLOCK_STATUS` (7)
 
     A block status query request. Length and offset define the range
-- 
2.21.0